1. Field of the Invention
The present invention relates to a biological component-measuring device and a method for calibrating a biological component-measuring device. More particularly, the present invention relates to a hygienic biological component-measuring device that is used for medical support devices and devices of this kind, which biological component-measuring device enables the operator to easily calibrate the entire device as well as the sensors thereof, and to attach a channel-carrying substrate to the device easily, which improves operability. The present invention also relates to a method for calibrating a biological component-measuring device, by which method the operator is able to calibrate the entire device easily while a biological component of a patient is being measured.
2. Description of the Related Art
An example of the biological component-measuring devices that have been conventionally used in the hospital is a glucose-measuring device by which the blood sugar level of a blood sample is measured. An example of the medical devices with a glucose-measuring device incorporated is an artificial endocrine pancreas device. Among the artificial endocrine pancreas devices, a type of artificial endocrine pancreas device that carries out a closed-loop control where components in the blood, which is a body fluid, of a patient, such as glucose, are measured continuously or at intervals, and liquid medicines such as glucose or insulin are injected into the patient based on the measurement in order to control the patient's conditions, requires accurate and safe operation during its use, often over a long period of time. Specifically, it is said that an artificial endocrine pancreas device should be capable of providing accurate measurement for a period from about four hours to about one week. It is very important for keeping the artificial endocrine device safe to periodically calibrate the sensors to obtain accurate and invariable measured values, and to calculate the amount of a liquid medicine necessary to be injected into the patient.
The glucose sensor sometimes outputs inaccurate values, which is caused by variation with time in the tubes passing through a peristaltic pump that is placed in various channels in an artificial endocrine pancreas device, which channels are also called tubes because they are typically made of soft and elastic tubes, especially in the tubes through which sampled blood is sent to the glucose sensor. The output of inaccurate values may also be caused by variation with time in the sensor per se; the output data or measured values themselves are inaccurate.
Therefore, the sensor of a conventional artificial endocrine pancreas device is periodically calibrated, which involves temporary stopping of sampling blood from the patient or injecting a liquid medicine into him/her. Specifically, for example, an indwelling needle kept in a vein of a patient is taken away from him/her and the artificial endocrine pancreas device is removed from him/her. Then, the sensors of the device are calibrated. After the completion of the calibration, the indwelling needle is inserted to his/her vein and kept in it again, which is followed by measurement of the blood sugar level of him/her with the artificial endocrine pancreas device. The measurement provides a value of the blood sugar level, based on which an amount of a liquid medicine is decided, and the liquid medicine in the amount is injected into him/her.
JP 58-152537 A discloses an invention for a blood substance-monitoring device that continuously measures substances in blood, which is an example of a biological component-measuring device whose sensors can be calibrated while sampling of body fluid of a patient is being continued. According to the invention, blood is continuously sampled through an indwelling cannula kept in a vein and substances included in the blood sample are measured. When the sensors are calibrated, the liquid to be sent to the sensors is switched from the blood sample to a calibrating liquid at a location just upstream of the sensors. After the completion of the calibration, the liquid to be sent to the sensors is immediately returned to the blood sample and the measurement is resumed. Blood being sampled during the calibration is disposed of through a waste liquid channel because the time period for the calibration is short. JP 52-135795 A teaches a method of calibrating sensors for glucose-measuring devices. This invention also employs the idea of switching liquids to be sent to the sensors. Specifically according to the invention, a calibrating liquid is introduced, by the switching, into the channel at a location near the sensors, downstream of a pump placed in the channel through which the blood sample is transferred. There are other relevant inventions. JP 58-198351 A discloses a method of measuring a specified component of the body fluid while a sample of the body fluid, such as blood, is being diluted several different times. JP 54-82885 A, JP 55-21905 A, and JP 56-28765 A disclose blood sugar level-controlling devices that employ a specified method of controlling the amount of insulin to be injected based on values obtained by continuous measurement of blood sugar level, and artificial endocrine pancreas devices.